1. Field of the Invention
The present invention relates to both a conductive anti-reflection film that functions as an anti-reflection film and that prevents an occurrence of an alternating electric field (AEF) and a cathode ray tube therewith formed on the outer surface of a face panel of a face plate.
2. Description of the Related Art
In recent years, it has been pointed out that electromagnetic waves that have generated in the vicinity of an electron gun and a deflection yoke leak out from a cathode ray tube such as a TV Braun tube or a computer monitor and adversely affect an electronic unit or the like that is disposed around the cathode ray tube. To prevent the electromagnetic waves (an electric field) from leaking from the cathode ray tube, it is required to decrease the surface resistance of the face panel thereof. So far, various surface treatment methods for preventing such a face panel from being charged have been proposed as in Japanese Patent Laid-Open Application Nos. Sho 61-118932, Sho 61-118946, and Sho 63-160140. With these methods, the AEF can be prevented.
To prevent the face panel from being charged, the surface resistance of the conductive film can be 1.times.10.sup.7 .OMEGA./.quadrature. or more. However, with such surface resistance, the AEF cannot be sufficiently prevented. To prevent the AEF, the surface resistance of the conductive film should be further decreased to 5.times.10.sup.2 .OMEGA./.quadrature..
As a method for forming a conductive film with a low surface resistance, a vapor growth method including PVD method, CVD method, and spattering method is known. For example, Japanese Patent Laid-Open Application No. Hei 1-242769 discloses a method for forming a low resistance conductive film by the spattering method. However, with the vapor growth method, large scaled equipment is required to form a conductive film. Thus, the cost of equipment becomes huge. In addition, with the vapor growth method, it is difficult to quantitatively produce such a film.
As a method for forming a conductive film, a solution of which transparent and conductive particles have been dispersed is coated on a substrate. The coated film is dried and sintered. This method is referred to as coating method or wet method. For example, a solution of which particles of tin oxide that contain Sb (referred to as ATO) or tin oxide that contain In (referred to as ITO) and a silica (SiO.sub.2) type binder have been mixed and dispersed is coated on a substrate. The resultant coated film is dried and sintered. As a result, a transparent conductive film can be prepared. Since the film thickness of the conductive film prepared in such a manner is designated as 1/4 of the designed wave length (namely, 1/4 .lambda.), the conductivity of particles of a conductive oxide with a large specific electric resistance is restricted. Thus, with particles of a conductive metal with a small specific electric resistance, the AEF can be effectively prevented.
However, even if a conductive film that contains metal particles is thin, since it absorbs rays in the visible region, when its film thickness increases, the transmissivity of rays particularly in the blue region (a short wavelength region) decreases, thereby degrading the luminance of the resultant cathode ray tube.
In addition, when a low surface resistance equivalent to the specific electric resistance is obtained with a conductive film that contains metal particles, the AEF can be sufficiently prevented without a decrease of the transmissivity of light. However, when the conductive film is formed, since part of metal particles is oxidized or present as metal ions, a sufficiently low surface resistance cannot be obtained.
In other words, it is difficult to reduce the cost of the conductive film that is produced in the dry process such as the spattering method. In addition, with the conductive film that is produced in the conventional coating method, the AEF cannot be effectively prevented without a decrease of the transmissivity of light.